1. Field of the Invention
This invention relates to a fuel nozzle and, more particularly, to a fuel nozzle having improved thermal resistance for eliminating or minimizing vaporization of fuel passing through the fuel nozzle.
2. Description of Related Art
Gas turbine engines commonly comprise a fuel nozzle for delivering fuel from a fuel supply source to an engine combustion apparatus.
It is not uncommon that the temperatures around the fuel nozzle can exceed 1000.degree. F. The presence of high temperatures around the fuel nozzle can cause the fuel passing through an inner passageway of the fuel nozzle to form granules of carbon on the walls of the inner passageway. The carbon formation on the walls of the inner passageway may cause the fuel nozzle to become clogged. Excessive temperatures can also cause the fuel in the fuel nozzle to gum up, thereby further causing the fuel nozzle to become clogged. In addition, when the temperature of the fuel reaches approximately 300.degree. F., the fuel may begin to vaporize in the inner passageway, thereby resulting in intermittent or non-continuous fuel delivery to the downstream end of the fuel nozzle.
Conventional fuel nozzles typically comprise a heat shield which surrounds a nozzle stem of the fuel nozzle and which cooperates with the nozzle stem to define an annular air gap which surrounds the nozzle stem. The purpose of the heat shield and air gap is to insulate the fuel nozzle from the high temperatures.
Although fuel nozzles have been provided with heat shields, the heat shield design may not be adequate to prevent vaporization of the fuel and the other problems mentioned above.